For the second year of this grant we have set the following goals: 1. To complete the study with respect to methionine and lysine, including the analysis and interpretation of the data. Consequently, at the end of this period we will be in the position to propose requirement values based on the results obtained. 2. To carry out the studies of tryptophan, threonine and valine. These amino acids, as stated in our original proposal, are considered also of first priority. It is anticipated that the study of other essential amino acids may also be included in this period, depending on the progress obtained.